Actually, a 223 with new heavy for cal bullets will drift equal to or better then a 308 at LR.
Playing around with the new 90's and performance should match maybe exceed even the 208/210gr loads used in F TR. I think if you look at the F TR landscape a year or so from now, the 223 will be making huge gains in the field.
At worst, it will always cost much less, kick way less, and keep barrels cooler during a relay. There is not alot of downside to this chambering in this sport.
The only downside to the 223 is the care needed in weighing charges. Small case, small error. however, with a good quality scale, the process is identical and you can shoot far more consistently with a light recoiling rifle then a heavy one.
The use of a 22LR should not be overlooked. Quite a few F class shooters train with a quality rimfire at reduced distances to maintain trigger time.
Precision shooting is all about your consistency and ability to launch the bullet well. Rimfires are brutal on gun control and being sloppy will show up on target in a big way.
Then the 2nd component is learning how to read the air. There is no substitute for launching lead and alot of it. It is pretty expensive even with a 223 to get the type of learning you need at the beginning of your career.
Think of shooting as thousands of rds of practise.
Good luck...
Jerry